From 2b4a5374ee12e8c7094cc8cd261366756cf6d81c Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Tue, 7 Feb 2023 22:42:03 +0100
Subject: [PATCH] Properly use location links for type hints of impl Future and
 its assoc type

---
 crates/hir-ty/src/display.rs           | 28 ++++++++++++++--
 crates/ide/src/inlay_hints.rs          | 15 ++++++---
 crates/ide/src/inlay_hints/bind_pat.rs | 30 +++++++++++++++--
 crates/ide/src/inlay_hints/chaining.rs | 45 ++++++++++++++++++++++++--
 4 files changed, 106 insertions(+), 12 deletions(-)

diff --git a/crates/hir-ty/src/display.rs b/crates/hir-ty/src/display.rs
index ae2162dd7c..1d4bf9ecb7 100644
--- a/crates/hir-ty/src/display.rs
+++ b/crates/hir-ty/src/display.rs
@@ -12,7 +12,7 @@ use hir_def::{
     find_path,
     generics::{TypeOrConstParamData, TypeParamProvenance},
     item_scope::ItemInNs,
-    lang_item::LangItem,
+    lang_item::{LangItem, LangItemTarget},
     path::{Path, PathKind},
     type_ref::{ConstScalar, TraitBoundModifier, TypeBound, TypeRef},
     visibility::Visibility,
@@ -731,8 +731,30 @@ impl HirDisplay for Ty {
                         )?;
                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
                     }
-                    ImplTraitId::AsyncBlockTypeImplTrait(..) => {
-                        write!(f, "impl Future<Output = ")?;
+                    ImplTraitId::AsyncBlockTypeImplTrait(body, ..) => {
+                        let future_trait = db
+                            .lang_item(body.module(db.upcast()).krate(), LangItem::Future)
+                            .and_then(LangItemTarget::as_trait);
+                        let output = future_trait.and_then(|t| {
+                            db.trait_data(t).associated_type_by_name(&hir_expand::name!(Output))
+                        });
+                        write!(f, "impl ")?;
+                        if let Some(t) = future_trait {
+                            f.start_location_link(t.into());
+                        }
+                        write!(f, "Future")?;
+                        if let Some(_) = future_trait {
+                            f.end_location_link();
+                        }
+                        write!(f, "<")?;
+                        if let Some(t) = output {
+                            f.start_location_link(t.into());
+                        }
+                        write!(f, "Output")?;
+                        if let Some(_) = output {
+                            f.end_location_link();
+                        }
+                        write!(f, " = ")?;
                         parameters.at(Interner, 0).hir_fmt(f)?;
                         write!(f, ">")?;
                     }
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index a9581db9ad..ac477339ec 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -294,10 +294,12 @@ fn label_of_ty(
     ) -> Result<(), HirDisplayError> {
         let iter_item_type = hint_iterator(sema, famous_defs, &ty);
         match iter_item_type {
-            Some((iter_trait, ty)) => {
+            Some((iter_trait, item, ty)) => {
                 const LABEL_START: &str = "impl ";
                 const LABEL_ITERATOR: &str = "Iterator";
-                const LABEL_MIDDLE: &str = "<Item = ";
+                const LABEL_MIDDLE: &str = "<";
+                const LABEL_ITEM: &str = "Item";
+                const LABEL_MIDDLE2: &str = " = ";
                 const LABEL_END: &str = ">";
 
                 max_length = max_length.map(|len| {
@@ -305,6 +307,7 @@ fn label_of_ty(
                         LABEL_START.len()
                             + LABEL_ITERATOR.len()
                             + LABEL_MIDDLE.len()
+                            + LABEL_MIDDLE2.len()
                             + LABEL_END.len(),
                     )
                 });
@@ -314,6 +317,10 @@ fn label_of_ty(
                 label_builder.write_str(LABEL_ITERATOR)?;
                 label_builder.end_location_link();
                 label_builder.write_str(LABEL_MIDDLE)?;
+                label_builder.start_location_link(ModuleDef::from(item).into());
+                label_builder.write_str(LABEL_ITEM)?;
+                label_builder.end_location_link();
+                label_builder.write_str(LABEL_MIDDLE2)?;
                 rec(sema, famous_defs, max_length, ty, label_builder)?;
                 label_builder.write_str(LABEL_END)?;
                 Ok(())
@@ -437,7 +444,7 @@ fn hint_iterator(
     sema: &Semantics<'_, RootDatabase>,
     famous_defs: &FamousDefs<'_, '_>,
     ty: &hir::Type,
-) -> Option<(hir::Trait, hir::Type)> {
+) -> Option<(hir::Trait, hir::TypeAlias, hir::Type)> {
     let db = sema.db;
     let strukt = ty.strip_references().as_adt()?;
     let krate = strukt.module(db).krate();
@@ -460,7 +467,7 @@ fn hint_iterator(
             _ => None,
         })?;
         if let Some(ty) = ty.normalize_trait_assoc_type(db, &[], assoc_type_item) {
-            return Some((iter_trait, ty));
+            return Some((iter_trait, assoc_type_item, ty));
         }
     }
 
diff --git a/crates/ide/src/inlay_hints/bind_pat.rs b/crates/ide/src/inlay_hints/bind_pat.rs
index da44d95297..f5b5c44737 100644
--- a/crates/ide/src/inlay_hints/bind_pat.rs
+++ b/crates/ide/src/inlay_hints/bind_pat.rs
@@ -330,7 +330,20 @@ fn main(a: SliceIter<'_, Container>) {
                                 ),
                                 tooltip: "",
                             },
-                            "<Item = impl ",
+                            "<",
+                            InlayHintLabelPart {
+                                text: "Item",
+                                linked_location: Some(
+                                    FileRange {
+                                        file_id: FileId(
+                                            1,
+                                        ),
+                                        range: 2643..2647,
+                                    },
+                                ),
+                                tooltip: "",
+                            },
+                            " = impl ",
                             InlayHintLabelPart {
                                 text: "Iterator",
                                 linked_location: Some(
@@ -343,7 +356,20 @@ fn main(a: SliceIter<'_, Container>) {
                                 ),
                                 tooltip: "",
                             },
-                            "<Item = &&str>>",
+                            "<",
+                            InlayHintLabelPart {
+                                text: "Item",
+                                linked_location: Some(
+                                    FileRange {
+                                        file_id: FileId(
+                                            1,
+                                        ),
+                                        range: 2643..2647,
+                                    },
+                                ),
+                                tooltip: "",
+                            },
+                            " = &&str>>",
                         ],
                     },
                     InlayHint {
diff --git a/crates/ide/src/inlay_hints/chaining.rs b/crates/ide/src/inlay_hints/chaining.rs
index 222ee59be8..0c54f084c1 100644
--- a/crates/ide/src/inlay_hints/chaining.rs
+++ b/crates/ide/src/inlay_hints/chaining.rs
@@ -440,7 +440,20 @@ fn main() {
                                 ),
                                 tooltip: "",
                             },
-                            "<Item = ()>",
+                            "<",
+                            InlayHintLabelPart {
+                                text: "Item",
+                                linked_location: Some(
+                                    FileRange {
+                                        file_id: FileId(
+                                            1,
+                                        ),
+                                        range: 2643..2647,
+                                    },
+                                ),
+                                tooltip: "",
+                            },
+                            " = ()>",
                         ],
                     },
                     InlayHint {
@@ -460,7 +473,20 @@ fn main() {
                                 ),
                                 tooltip: "",
                             },
-                            "<Item = ()>",
+                            "<",
+                            InlayHintLabelPart {
+                                text: "Item",
+                                linked_location: Some(
+                                    FileRange {
+                                        file_id: FileId(
+                                            1,
+                                        ),
+                                        range: 2643..2647,
+                                    },
+                                ),
+                                tooltip: "",
+                            },
+                            " = ()>",
                         ],
                     },
                     InlayHint {
@@ -480,7 +506,20 @@ fn main() {
                                 ),
                                 tooltip: "",
                             },
-                            "<Item = ()>",
+                            "<",
+                            InlayHintLabelPart {
+                                text: "Item",
+                                linked_location: Some(
+                                    FileRange {
+                                        file_id: FileId(
+                                            1,
+                                        ),
+                                        range: 2643..2647,
+                                    },
+                                ),
+                                tooltip: "",
+                            },
+                            " = ()>",
                         ],
                     },
                     InlayHint {